Pre-eclampsia and eclampsia are the most important causes of maternal morbidity and mortality in the USA, Scandinavia, Iceland, Finland and the UK. Unfortunately the pathophysiology of pre-eclampsia is still poorly defined. Nitric oxide (NO) generated by glyceryl trinitrate (GTN) can attenuate the vasoconstrictor effects of endothelin-1 and other vasopressors on fetal-placenta circulation. Consequently, we hypothesize that GTN administration during pregnancy might restore the reduced NO levels, and thus protect the mother and fetus.